We show the generation of a strong phase-matched third harmonic in a simple parallel nematic liquid crystal cell. A single laser beam of femtosecond pulses is used to deform the internal structure of the molecular orientation distribution, and to generate the third harmonic from the twisted structure that is formed. Up to ${10}^{-5\mathrm{}}$ of the laser power was converted to the third harmonic, in a volume as small as 5 $\mu {\mathrm{m}}^3$.

• Received 18 November 1998

DOI:https://doi.org/10.1103/PhysRevLett.82.3046